1. Field of the Invention
The present invention relates to a method for preparing finely divided silicone rubber particles. In particular, this invention relates to a method for preparing a finely divided silicone rubber powder containing large amounts of various types of particulate additives such as magnetic metal powders, electrically conductive powders, and reinforcing silica fillers.
2. Description of the Prior Art
The preparation of spherical silicone rubber particles by dripping a low-viscosity liquid silicone rubber composition is dripped under free-fall conditions quiescent water curing the resultant dripped-in material is taught in Japanese unexamined published application (Kokai) Number 61-223032 [223,032/86]).
However, because this method does not allow the incorporation into the liquid silicone rubber composition of large quantities of the various types of particulate additives which are used to provide silicone rubbers with particular physical properties, the problem arises that one cannot obtain silicone rubber particles having special capabilities or an excellent mechanical strength.
U.S. Pat. No. 4,749,765 which issued on Aug. 11, 1987 to one of the three inventors named on the present application and one other, and is assigned to the same assignee as the present application, teaches a method for preparing cured silicone rubber in the form of a powder by spraying the ingredients of a heat-curable silicone rubber composition into air heated to a temperature of from 80.degree. to 200.degree. C.
U.S. Pat. No. 4,743,670, which issued on May 10, 1988 to two of the three inventors named on the present application and one other and is assigned to the same assignee teaches a method for preparing a cured silicone rubber powder by dispersing a heatcurable liquid silicone rubber composition into water at a temperature of from 0.degree.-25.degree. C. and then dispersing this dispersion into water heated to a temperature above 25.degree. C. to form the cured silicone rubber powder.
None of the aforementioned methods are capable of forming a powdered form of silicone rubber containing 100 parts by weight or more per 100 parts of curable liquid silicone rubber composition of a particulate additive such as a metal powder or a reinforcing fillers.